Gemini CLI v0.54.0

PR Automation & Antigravity Agent: Integrated the Antigravity agent runner with dual-locking Firestore concurrency controls to secure the PR generator ( #28434 , #28432 by @joneba-google).

Caretaker Triaging & Security: Enhanced caretaker triage to post comments prior to auto-closing issues and sanitized issue titles under untrusted context ( #28411 , #28352 by @chadd28).

Security and Session Robustness: Prevented cleartext credential leakage by enforcing HTTPS, rotated session IDs on model fallbacks, and skipped merged function-response turns in active loops ( #28517 by @amelidev, #28565 by @adamfweidman).